Initial doxysphinx documentation

[MathiasMagnus]

This is the initial implementation of a sphinx based documentation using doxysphinx, which takes doxygen docs unmodified and reformats it into sphinx-like output for a smoother experience when hooked up to ROCm docs.

Ultimately the results should be hosted on readthedocs, however there is an outstanding issue of removing the dependency on npm (sass) which is not a Python module. There are multiple ways to go around this, but non has reached rocm-docs-core yet.

[MathiasMagnus]

Empty page removed, README/index.md deduplicated.

[saadrahim]

@MathiasMagnus please take a look at the PR and ensure it builds on RTD.